Caldesmon is a thin filament calmodulin-binding protein which appears to play a role in the regulation of actin-myosin interaction in smooth muscle and nonmuscle cells. There are at least 2 isoforms of caldesmon, a high molecular weight form found primarily in smooth muscle and a lower molecular weight form found mainly in nonmuscle cells. We are attempting to clone and sequence the caldesmon found in chicken intestinal brush border. Once this is accomplished we would like to use bacterial expression vectors and study the expressed protein as well as genetically engineered variants.